A high-power helicon like this could fire a beam of magentised particles

Advocates of a propulsion idea for spacecraft claim that it would enable a 90-day round trip to Mars.

Using current technology, it would take astronauts about 2.5 years to travel to Mars, conduct their mission and return to Earth, US scientists estimate.

It would use a space station to fire a beam of magnetised particles at a solar sail mounted on a spacecraft.

This plasma beam would then make use of repulsive forces to propel the spacecraft along at high speeds.

Rather than a spacecraft having to carry these big powerful propulsion units, you can have much smaller payloads

Robert Winglee, University of Washington

The speeds possible would increase with the size of the plasma beam, says the team behind the concept - which is called Mag-Beam.

Project leader Robert Winglee, of the University of Washington, US, estimates that a control nozzle 32m wide would generate a plasma beam capable of propelling a spacecraft at 11.7km/second.

"We're trying to get to Mars and back in 90 days. Our philosophy is that, if it's going to take two-and-a-half years, the chances of a successful mission are pretty low," he said.

However, to make such high speeds practical, another plasma unit would have to be stationed on a platform at the other end of the trip to apply brakes to the spacecraft.

Reduced burden

"Rather than a spacecraft having to carry these big powerful propulsion units, you can have much smaller payloads," Professor Winglee explained.

He added that these units could be placed around the Solar System by Nasa missions currently in the pipeline. Units placed further out in the Solar System would use nuclear power to create the ionised plasma, while those closer to the Sun would be able to use electricity generated by solar panels.

The beam of magnetic particles interacts with a solar sail

Mars is an average of 77 million km (48 million miles) from Earth, although this distance can vary greatly depending on where the two planets are in their orbits around the Sun. At that distance, a spacecraft travelling at 11.7km/second would take more than 76 days to get to the Red Planet.

Professor Winglee said he was working on ways to squeeze even greater speeds out of the Mag-Beam technology so that the round trip could be accomplished in three months.

Nasa has invested $75,000 (£41,500) in a six-month study to validate the concept and identify the challenges involved in developing it. It has invested the same amount in 11 similar proposals.

Projects that make it through this phase are eligible for as much as $400,000 (£221,000) more over two years.

A Mag-Beam test mission could be possible within five years if financial support remains consistent, Professor Winglee said.